Hopper-type railway cars are used to transport lading which is discharged from the hopper car through outlet gate assemblies mounted on discharge openings at the bottom of the car. Each gate assembly includes a door plate and a drive for moving the plate between opened and closed positions. When closed, the plate prevents discharge of lading. When the plate is opened, the lading is free to discharge through the assembly.
Conventional gate assemblies include rack and pinion drives used to shift the plate between the open and closed positions. Typically, a pair of racks are secured to the lower surface of the plate and engage pinion gears mounted on a transverse drive shaft. The opposed ends of the drive shaft extend to opposite sides of the gate assembly and carry capstans. The assemblies are opened or closed by rotating a capstan in a appropriate direction to rotate the pinion gears on the drive shaft and the plate in an appropriate direction.
The conventional gate assembly includes a latch which engages the edge of the plate after it has been moved to the fully closed position by the drive. Rotation of a capstan to move the plate to the closed position does not automatically engage the latch. The plate must be closed and then the latch is manually moved to engage the plate and hold the plate fully closed. Typically, the yard worker closes the plate by rotating the capstan. The worker must then manually engage the latch. The latch must also be manually disengaged prior to moving the plate from the closed to the opened position.
In July, 1992, the Association of American Railroads revised the Standard S-233-92 governing latching systems for outlet gate assemblies for hopper-type railway cars. The revised standard requires that the latch/unlatch functions be integrated into the discharge gate operating mechanism. Rotation of a capstan in a direction to open the plate must first unlatch the plate and then move the plate from the closed to the open position.
A prior outlet gate assembly, meeting the revised AAR standard S-233-92 provides lost motion connections between the operating shaft and the pinion gears which are meshed with racks on the bottom surface of the plate. The drive shaft carries a cam which is engageable with the plate latch when the plate is in the closed position. A capstan is directly mounted on each end of the drive shaft and rotates with the drive shaft. Initial rotation of the drive shaft collapses lost motion connections between the shaft and the pinion gears without rotating the gears or moving the plate from the closed position while moving the cam into engagement with the latch to unlatch the plate. After the plate has been unlatched, the lost motion connections are collapsed and continued rotation of the drive shaft rotates the pinion gears to move the unlatched plate to the open position. The lost motion connections used in this gate assembly are located on the drive shaft at relatively inaccessible locations under the assembly frame. In this type of a gate assembly, the pinion gears are loose on the drive shaft so that it is difficult for workers to mount the drive shaft on the frame with the pinion gears properly meshed and timed with the racks on the plate for proper integrated unlatching during opening of the gate. Further, the pinion gears with lost motion connections are located under the frame between frame extensions. It is difficult for a worker to inspect the lost motion connections to make sure that they are free of track debris and operate properly. Debris captured within the lost motion connections could prevent proper integrated operation of the gate assembly.